Department of Anesthesiology - Residents Section

Anesthesia Knowledge - Elderly Anesthesia

Anesthesia for the Elderly

"Elderly" or "geriatric" - older than 65.

"Aged" - older than 80.

Number of elderly rises and number of aged comprises 10% of the elderly.

Greater risk of perioperative complications because of age-related concomitant diseases and a generalized decline in organ function, which may manifest only with the added stress of the perioperative period.

Age-related concomitant diseases

Systemic hypertension

CAD

CHF

PVD

COPD

Anemia

Renal disease

Liver disease

Diabetes mellitus

Subclinical hypothyroidism

Arthritis

Dementia

Emergency surgery particularly dangerous because it doesn't allow for optimization and control of co-existing disease.

Psychological factors play important role: fear of the loss of independence, etc.

CNS

Brain size decreases, weight is about 20% less by age of 80. Attrition of neurons, particularly those that synthesize neurotransmitters. Requirements for the drugs that act on CNS decreases.

PNS

Slowing of electrical conduction along efferent motor pathways. Increase in number of cholinergic receptors at the neuromuscular junction, it offsets the age-related decrease in the number and density of the motor neurons.

Non-depolarizers have prolonged time of onset and duration of action, if elimination is dependent on renal or hepatic clearance, but dose rerquirements are similar to young adults.

Decreased segmental dose requirements for epidural anesthesia.

Pharmacology

Increased variations in pharmacodynamics and pharmacokinetics lead to increased incidence in adverse drug reactions. Changes in volume of distribution are common.

Causes of increased elimination half-times of drugs.

Decreased clearance:

Renal blood flow

Glomerular filtration rate

Hepatic blood flow

Hepatic microsomal enzyme activity

Increased volume of distribution:

Body fat content

Protein binding

Hypnotics.

Thiopental. Sensitivity increased due to decreased volume of distribution, and as a result, higher plasma concentration delivered to the brain. Brain sensitivity doesn't change with age. Dose decrease by 15% in 80 years old as compared to 20 years old to achieve the same effect.

Midazolam. Big difference in intrinsic brain sensitivity to the drug requires decrease in dose by 30% to 60% in 60-year-old and 80-year-old respectively, as compared to 20-year-old.

Opioids.

Fentanyl. Dose decreased by 50% in 85 y.o. as compared to 20 y.o. to produce the same effect due to pharmacodynamic changes. Alfentanyl. Pharmacokinetics doesn't change with age. Dose decrease by 50% due to pharmacodynamic changes and increased brain sensitivity to any concentration.

Sufentanyl. Highly bound to alpha-1-acid glycoprotein, as it is increased in the elderly, free fraction of the drug is decreased with age, thus suggesting the decrease in potency. However, clinical experience suggests that brain sensitivity to opioids in elderly is increased, thus dose should not be altered.

Neuromuscular blocking drugs.

Pancuronium. Decrease in renal function slows clearance.

Vecuronium. Slight decrease in clearance suggests about 10% decrease in dose. Changes in sensitivity of the neuromuscular junction to neuromuscular blockers do not occur.

Atracurium and Cisatracurium. Both ester hydrolysis and Hoffman elimination are not affected by age. Intrinsic potency of the drugs is not affected either.

Management of anesthesia

Fast and complete recovery of mental function is of utmost importance.

Preoperative evaluation and preparation.

Co-existing diseases. Alcoholism possible.

Changes in mental function - cardiac or pulmonary pathology should be excluded.

Drug history, interactions.

Detailed explanation to reduce anxiety, rather than benzodiazepines, in the preoperative period.

Postoperative mental dysfunction (delirium)

One of the most common complications in elderly. Incidence about 10%-15% in elderly undergoing surgery. Interval delirium occurs after a lucid interval of one or more days after an operation and is the most frequent form of postoperative delirium in elderly patients. Emergence delirium occurs within minutes of regaining consciousness and is more often present in children.

Clinical features include disorders of attention, cognition, sleep-wake cycle, and psychomotor behavior. Symptoms are usually increased during periods of darkness. Disorientation of time, place, and person are common. Delirious patients may endanger themselves by inflicting self-injury or pulling out medical catheters.